Anthony Weiner / Spencer Platt Getty Images

by Catalina Camia and John Bacon , USA TODAY

by Catalina Camia and John Bacon , USA TODAY

Anthony Weiner vowed Sunday to stay in the New York City mayor's race, as he confirmed his campaign manager quit and his top rival said he was not qualified to lead the nation's most populous city.

Weiner said that campaign manager Danny Kedem resigned after revelations came out last week that Weiner continued to send salacious messages online to women, even after resigning from Congress in 2011.

"We knew this would be a tough campaign," Weiner said while campaigning in Brooklyn. "We have an amazing staff, but this isn't about the people working on the campaign. It's about the people we're campaigning for."

The tumult in Weiner's staff was first reported by The New York Times. Hours later, City Council Speaker Christine Quinn repeated criticism on NBC's Meet the Press that Weiner has displayed "a pattern of reckless behavior, an inability to tell the truth and a real lack of maturity."

Quinn, who has a 9-point lead over Weiner, went beyond those comments when pressed if Weiner had disqualified himself by admitting he continued to send lewd messages after such behavior forced him to quit the U.S. House. As she noted her accomplishments on the City Council, Quinn pointed out that Weiner only managed to get one bill passed during his 12 years in Congress.

"Has he disqualified himself? Yes, he disqualified himself, but not just because of these scandals," Quinn said. "He didn't have the qualifications when he was in Congress."

Rep. Pete King, R-N.Y., who served with Weiner in Congress, said on CNN's State of the Union program that Weiner is "not psychologically qualified to be mayor of the city of New York."

Weiner revealed Thursday that he sent explicit texts to as many as 10 women, including three after he left Congress. They apparently include Sydney Leathers, 23, of Princeton, Ind., who revealed that Weiner had sent nude photographs to her -- and that they engaged in phone sex -- months after his resignation.

Weiner has steadfastly rebuffed calls that he quit the mayor's race, which have come from rivals such as Bill de Blasio and top Democratic leaders such as national party Chairwoman Debbie Wasserman Schultz and House Minority Leader Nancy Pelosi.

Kedem was hired earlier this summer, just a few weeks ahead of Weiner's surprise announcement that he would attempt a political comeback after his sexting scandal. The news rocked the mayor's race, and Weiner immediately soared to the top of public opinion polls, either coming ahead of Quinn or finishing a close second to her in the field of seven Democrats.

Kedem was a field organizer for Hillary Rodham Clinton's 2008 presidential campaign and managed Democrat Mark Murphy's unsuccessful congressional bid last year against Republican Rep. Michael Grimm on Staten Island.

While Quinn repeated Sunday that it is ultimately up to New York City voters to decide Weiner's fate, there appears to be a division among those who would weigh in on the Democratic primary. Forty-three percent of Democratic primary voters say Weiner should quit the race, while 47% say he should continue running for mayor, according to the survey released Thursday by NBC 4 New York, The Wall Street Journal and the Marist Instiitute for Public Opinion.

Douglas Muzzio, a professor in the public affairs school at Baruch College, said Weiner's campaign is essentially over.

"Stick a fork in him, he's done," Muzzio said Sunday in a telephone interview. "He's really got no (campaign) organization. Anthony Weiner has proven he is incapable of running a campaign."

Party primaries are Sept. 10. If no candidate gets more than 40% of the vote, a runoff will be held Oct. 1.